Pulverizing mill



Sept. 21, 1943. JOHNSON 2,329,910

` PULVERIZING MILL Filed Dec. l1, 1941 MR mll'llm Patented Sept. 2l, 1943*" UNITED STATES PATT] formica PULvEmzmG MILL stanley Johnson. Stockport, lummm:

Application December 11, 1941, Serial No.

V In Great Britain January 27, 1941 5 claims. (cia3-11) This invention relates to pulverizingapparatus' for the reduction of friable materials to a ne impalpable state by impact. One application of the invention is to the formation of soap powders, but the invention is equally applicable to other uses where pulverlzation by impact is possible, and includes the pulverization of harder types of material, such as resin, glass and the like.

Pulverizing mills as heretobefore known for the production oi' line powders, 'and comprising a series of beaters rotating'within a sieve, have been characterized by a small areaofsieve surthe beaters when the sieves are choked, and may become rock-like, requiring to be chipped from the sieves.

The object of the present invention is to provide improved pulverizing mills of the centrifugal type (i. e. having rotating beaters within a. sieve) which-eliminate the above-mentioned disadvantages.

According to this invention,` a pulverizing mill comprises a relatively large, vertically-disposed, open-ended cylindrical sieve or screen, a series of beaters co-axially mounted within the sieve or screen, at diierent points in its length, for simultaneous rotation, means for rotating such beaters at high speed, and means for directing the unpulverized material into the open upper end of the screen. Usually, the sieve will be housed within an enclosing wall or chamber, and

so as to leave an enclosed cavity around its outer the material which passes and a hopper will be prosurface to receive through the screen,

vided at the upper end of the mill for receiving lthe unpulverized material and for directing it to the centre of the space in which the beaters rotate.

In preferred embodiments of the invention, the axle or shaft which carries the beaters is supported in a removable footstep bearing, and is detachably coupled to the driving shaft of a motor or other. source of power, mounted at the upper end of the mill, so that by removing such mentioned, tend to I say by means neness according'to the work to be done.

The material may be fed to the hopper by hand, of a scoop, or automatic means may be provided to feed a constant regular suphopper. Suitable colcoarser grade will suit.

In the accompanyingl drawing:

Fig. 1 is a part-sectional front elevation of a pulverizing mill characterized as one example of the invention;

Fig. 2 is a sectional plan taken on the line 2 2 of Fig. l;

Fig. 3 is a sectional perspective view of apart shown in Fig. 2;

Fig. 4 is an enlarged view of one of the beaters appearing in Fig. 1, and showing its association with the screen; whilst Fig. 5 is a sectional plan taken on the line 5 5 The example illustrated has been designed and tested for use mainly in pulverizing a sulphonated compound for use as a soap powder. It comprises at the lower part a box or cupboard to receive the pulverized material, and at the upper part a beating chamber mounted thereon, this being open at the top and provided with a hopper to receivey the material which is to be milled.

The said base is made up of the box or chamber i, having a removable side door 2, held in position by the pairs of pivoted latches 3. The door will be as close a t as possible in its recess, and will have a felt or like packing to prevent escape of dust. Mounted on the top of the box i, by means of the lugs 4B, is a cylindrical chamber li, to the upper end of which is secured the bridge 5, carrying an electric motor 6. The shaft 1 of the motor extends downwardly through the bridge ,and terminates in a coupling 8.

Arranged co-axially within the chamber 4 is an open-ended cylindrical wire mesh screen 9 of woven steel wire. each end of the screen being fitted with a rubber or like resilient packing member I0. At its lower end the screen 9 rests on a cross-shaped frame II, being positioned thereon by the lugs I2, whilst at its upper end the screen fits below: a hopper I3 having4 the downwardly-projecting ange I4. The hopper I3 is made in two parts, as is seen more particularly in Fig. 2, s'o as to be more easily removable, and is secured to the upper end of the outer cylinder 4, a felt packing being provided at the joint to exclude dust.

At the centre of the cross-shaped frame II, is a ball-bearing footstep I5, which receives the lower end of the beater shaft I6, whose upper end is held in the coupling 8 on the motor shaft 1. This beater shaft I6 is on the axis of the screen 9 and carries a number of beater arms I1, which are spaced equally along the shaft and are also spaced equally around the shaft (see Fig. 5). Each beater comprises bers shaped at their inner ends to embrace the shaft, and the two members being clamped to the shaft by suitable bolts and nuts or the like. The beaters extend to Within a short distance of the screen, but do not touch it.

In order to prevent the inserted material flying back through the feed opening in the hopper I3, a cone-shaped guard I8 is fitted to the beater shaft I6 just below that opening. Moreover, one or more of the beaters may be slightly twisted to create an axial draught, and the box I will be fitted with the dilatable bag I9 to allow escape of air whilst retaining any dust caught in the air stream.

As shown in Fig. 1, the lower end of th'e screen may be fitted with a removable bag to catch any material not passing through the screen, but this will not always be necessary. By increasing, the length of the sieve, and adding to the number of beaters, the uniform pulverizing ofthe material may in most cases be ensured, but where these changes are not convenient, the material caught by the bag 20 may be fed through the mill a second time, or may be kept separate from the remaining finer material, for use for other purposes.

The beaters and the screen may be plated with chromium or similar hard non-corrosive material, but it will be found that even when not plated, the machine can be run for prolonged periods without becoming clogged. However, it will be seen from the drawing that cleaning of the machine, when required, may be effected very easily; for by removing the securing bolts for the cross-shaped frame Il, that frame may dropped out of position, and when the coupling 8 is loosened, the beater shaft and beaters may be dropped for cleaning purposes, as also may the screen 9. Similarly, the replacing of a screen by one of different mesh may be carried out quickly and easily.

The rubber or other resilient packing at the ends of the screen 9 eliminates audible rattle whilst the mill is working, but allows a slight vibration of the screen which assists in keeping it unclogged. l

The following particulars of size etc. have been found satisfactory in use, and are quoted merely a pair of flat metal memouter wall, a hopper on as being representative of many variations, according to the substance to be dealt with:

Length of screen inches 32 Diameter of screen do-- 12 Mesh of screen d0. 1,-1/8 Diameter of outer casing do 20 Number of beaters '7-10 Horse power of motor 21/2-31/2 Speed of motor R. P. M 3,000 Capacity of mill From 8 cwt. per hour Owing to the relatively greater screen capacity, and to the lower end of the sieve being open, clogging does not occur, even with gummy substances such as are used in the manufacture of soap powders, and a constant feed is possible. Moreover, as little or no dust is emitted from the mill, there being no thrashing, of obstructed material, the mill may be operated in an open room without discomfort.

In an alternative arrangement, not illustrated. the box I could be dispensed with, at least as a receiving chamber, and the sifted material be allowed to collect in the cylindrical chamber 4, such chamber being enlarged for that purpose. In such case, the material not passing through the screen would be allowed tov fall into a suitable receiver below the screen, so as not to foul the rotating beaters.

When the powders to be produced are of a very fine degree, as for example with talcum powder, a silk screen or other suitable textile membrane may be placed around the wire mesh screen 9, or may be sandwiched between two screens, or in some cases may take th place of the screen.

Again, when the materials to be pulverized are of a coarse hard nature, as in the case of beans, maize, other provender materials, the effect of the beaters may be enhanced by their being serrated or ribbed, or made with pointed protuberances on their striking faces.

In order further to facilitate the removal of the screen 9, for cleaning or replacement purposes to give access to the beaters, the outer casing 4 may be provided with one or more doors or like removable parts, or may consist of removable panels secured to a fixed frame or skeleton. In all such cases, suitable dust-proof packings will be provided if required.

What I claim is:

1. A pulverizing mill comprising an enclosing the upper end of such wall, a removable frame across the lower end of the enclosure, a cylindrical sieve or screen within the enclosure clamped against the hopper by the frame, a shaft supported by its lower end on the frame and carrying a series of longitudinallyand angularly-spaced beater arms extending to within a short distance of the screen, and means detachably coupled to the upper end of the shaft for rotating it at high speed; the shaft beaters and screen all being removable from the enclosure by merely removing the said frame and detaching the coupled driving means.

2. A pulverizing mill comprising a cylindrical imperforate open-ended wall, a hopper mounted in the top end of such wall, a frame removably mounted in the lower end of such wall, a substantially cylindrical perforated sieve or screen sandwiched between the frame and hopper, within the wall, a footstep bearing on the frame, an electric motor mounted above the hopper, a shaft supported in the footstep passing through the hopper, and detachably coupled to the motor, a series of beaters secured along and around the shaft with their extremities near but not touching the sievel and a box-like base as a support, such base communicating with the space between the imperforate wall and the sieve; and having a removable bag on the lower end of the sieve and of the same shape at its mouth as the base of the sieve to isolate unsieved matter falling through such lower end.

3. In a pulverizing mill a cross-shaped frame at the bottom of the mill with thrust bearing at its centre and an upstanding lug at the end of each arm; a hopper of inverted cone shape at the top of the mill with depending lugs thereon; a

single perforated cylindrical screen between the frame and the hopper and positioned co-axially with the bearing by such upstanding and depending lugs; resilient packings between the several lugs and the screen; means connecting the frame to the hopper to hold the screen captive between the frame land hopper and a, support for such connecting means to hold the assembly 20 with the screen axis vertical.

4. In a pulverizing mill, an assembly according to claim 3, wherein the connecting means comprises an enclosing wall, a. bridge member across such Wall above the hopper, a bearing in the bridge member co-axial with the thrust bearing of the frame, a beater shaft journalled in the said bearings, and an electric motor mounted on the bridge member for driving the shaft, and a detachable coupling for drivingly connecting the motor to the shaft.

5. In a pulverizing mill an assembly according to claim 3 wherein the connecting means is secured to the support independently of the secur- .ing of the frame to the connecting means and wherein the 4support has an aperture below the connecting means through which the frame and screen may be withdrawn whilst the connecting means remains in position.

STANLEY JOHNSON. 

